Create Linked List in Reverse
#include <stdio.h>
#include <stdlib.h>
typedef struct node {
int data;
struct node* next;
} node;
void insert_node(node** head, int val, int position);
void insert_node(node** head, int val, int position)
{
struct node *curr = *head, *tmp_node = NULL;
int count = 1;
tmp_node = (node*)malloc(sizeof(node));
if (tmp_node == NULL) {
printf("Memory allocation is failed:");
return;
}
tmp_node->data = val;
tmp_node->next = NULL;
if (*head == NULL) {
// List is empty, assigning head pointer to tmp_node
*head = tmp_node;
return;
}
if (position == 1) {
// Inserting node at the beginning of the list
tmp_node->next = *head;
*head = tmp_node;
return;
}
while (curr && count < position - 1) {
curr = curr->next;
count++;
}
if (position > (count + 1)) {
printf("\n position doesn't exists in the list ");
return;
}
if (count + 1 == position && curr->next == NULL) {
// Inseting node at the end of the list
curr->next = tmp_node;
return;
}
// Inserting node in the list at given position
tmp_node->next = curr->next;
curr->next = tmp_node;
}
void print_list(node* head)
{
printf("\nList elements:\n");
while (head) {
printf("%d ", head->data);
head = head->next;
}
printf("\n");
return;
}
int main()
{
int num_nodes, value, index, position;
node* head = NULL;
printf("Enter the no. of nodes to create list: ");
scanf("%d", &num_nodes);
for (index = 1; index <= num_nodes; index++) {
printf("Enter node data for position %d in the list: ", index);
scanf("%d", &value);
insert_node(&head, value, index);
}
print_list(head);
printf("\nInsert the element at 1st position: ");
scanf("%d", &value);
insert_node(&head, value, 1);
// We have inserted one more element, hence num_nodes get increased by 1
num_nodes += 1;
print_list(head);
printf("\nInsert the element at last position: ");
scanf("%d", &value);
insert_node(&head, value, num_nodes + 1);
// We have inserted one more element, hence num_nodes will get increased by 1
num_nodes += 1;
print_list(head);
printf("\nInsert the element at any position in the list\n");
printf("Enter the position: ");
scanf("%d", &position);
printf("Enter the element value: ");
scanf("%d", &value);
insert_node(&head, value, position);
// We have inserted one more element, hence num_nodes will get increased by 1
num_nodes += 1;
print_list(head);
return 0;
}
Output
Enter the no. of nodes to create list: 5
Enter node data for position 1 in the list: 11
Enter node data for position 2 in the list: 22
Enter node data for position 3 in the list: 33
Enter node data for position 4 in the list: 44
Enter node data for position 5 in the list: 55
List elements:
11 22 33 44 55
Insert the element at 1st position: 10
List elements:
10 11 22 33 44 55
Insert the element at last position: 20
List elements:
10 11 22 33 44 55 20
Insert the element at any position in the list
Enter the position: 4
Enter the element value: 40
List elements:
10 11 22 40 33 44 55 20
Display Linked List in Reverse
#include <stdio.h>
#include <stdlib.h>
struct node{
int data; // data field
struct node *next;
};
void display(struct node* head){
struct node* current=head; // current node set to head
printf("traversing the list...\n");
while(current!=NULL){ //traverse until current node isn't NULL
printf("%d ",current->data);
current=current->next; // go to next node
}
}
void reverse_display(struct node* head){
if(head){
//recursive call to display in reverse order
reverse_display(head->next);
printf("%d ",head->data);
}
}
struct node* creatnode(int d){
struct node* temp=malloc(sizeof(struct node));
temp->data=d;
temp->next=NULL;
return temp;
}
int main(){
printf("creating the linked list by inserting new nodes at the end\n");
printf("enter 0 to stop building the list, else enter any integer\n");
int k,count=1,x;
struct node* curr,*temp;
scanf("%d",&k);
struct node* head=creatnode(k); //buliding list, first node
scanf("%d",&k);
temp=head;
///////////////////inserting at the end//////////////////////
while(k){
curr=creatnode(k);
temp->next=curr;//appending each node
temp=temp->next;
scanf("%d",&k);
}
display(head); // displaying the list
printf("\ndisplaying in reverse order...\n");
reverse_display(head);//display in reverse order
return 0;
}
Output
First run:
creating the linked list by inserting new nodes at the end
enter 0 to stop building the list, else enter any integer
1 2 3 4 0
traversing the list...
1 2 3 4
displaying in reverse order...
4 3 2 1
Second run:
creating the linked list by inserting new nodes at the end
enter 0 to stop building the list, else enter any integer
34 55 2 4 76 -8 6 0
traversing the list...
34 55 2 4 76 -8 6
displaying in reverse order...
6 -8 76 4 2 55 34
